problems to live by

35. Cars cross a certain point in the highway in accordance with a Poisson process with rate lambda = 3 per minute. If Reb blindly runs across the highway, then what is the probability that she will be uninjured if the amount of time that it takes her to cross the road is s seconds? (Assume that if she is on the highway when a car passes by, then she will be injured.) Do it for s = 2, 5, 10, 20.